Method for impregnating running paper with moisture

ABSTRACT

Electrostatically impregnating sprayed liquid particles onto a moving sheet of paper. An attracting electrode, electrically insulated from ground, is maintained at a high potential. A predetermined number of spray nozzles are connected to a liquid supply source maintained at ground potential, and these spray liquid onto the moving paper while the paper is moved along the electrode, the nozzles and electrode being on opposite sides of the paper. The nozzles are spaced from the electrode, and they are arranged in parallel across the paper so as to cover the full paper width with liquid particles.

United States Patent Tamotsu Watanabe [72] Inventor Rm. 606, Marunouchi Bldg., Marunauchi, Chiyoda-ku, Tokyo, Japan,

[21] App1.No. 760,815

[22] Filed Sept. 19, 1968 [45] Patented Dec. 7, 1971 [32] Priorities Dec. 12,1967

[33] Japan Apr. 23, 1968, Japan, No. 43/26797 [54] METHOD FOR IMPREGNATING RUNNING PAPER WITH MOISTURE 11 Claims, 1 1 Drawing Figs.

[52] US. Cl. 117/93.4 NC, 117/l05.3, 117/152, 118/630 [51] Int. Cl B05b 5/02 [50] Field of Search 117/93.4 R,

[56] References Cited UNITED STATES PATENTS 1,861,47 1932 Hopkins et al particles.

1,889,851 12/1932 Crane ll7/l52X 2,226,709 12/1940 Colbert 117/152 X 3,222,209 12/1965 Brundige et a1 117/152 X 3,467,541 9/1969 Aronsson et al 1 17/934 3,484,275 12/1969 Lewicki, Jr. l17/93.4

Primary Examiner-Ralph S. Kendall Attorney-Owen, Wickersham & Erickson ABSTRACT: Electrostatically impregnating sprayed liquid particles'onto a moving sheet of paper. An attracting electrode, electrically insulated from ground, is maintained at a high potential. A predetermined number of spray nozzles are connected to a liquid supply source maintained at ground potential, and these spray liquid onto the moving paper while the paper is moved along the electrode, the nozzles and electrode being on opposite sides of the paper. The nozzles are spaced from the electrode, and they are arranged in parallel across the paper so as to cover the full paper width with liquid PATENTEUnEc H97! 3,625,743

SHEET 2 BF 3 INVENTOR BY M $21M ATTORNEY PATENTEDUEC 7197! 3625743 SHEET 3 BF 3 BY O U/M Mq ATTORNEY METHOD FOR IMPREGNA'IING RUNNING PAPER WITH MOISTURE This invention relates to a method and an apparatus for electrostatically depositing and mechanically impregnating atomized water particles or the like on a moving sheet of paper, in order to bring the whole area of the paper to a homogeneous predetermined moisture content.

The paper industry has long cherished the desire of giving a proper percentage of homogeneous moisture content to a moving strip or sheet of paper, for the purpose of improving quality and printing fitness of the paper, and various attempts have been made to attain the requirement. For example, in one prior art method droplets from a brushroll that is partly immersed in water are mechanically atomized and sprayed onto the surface of the moving paper. In another prior art method, highly pressurized water is ejected through tiny orifices and impacted upon a baffle plate for atomization, and the thus-atomized water particles are then sprayed onto the surface of the moving paper. A third prior art method employs compressed air for atomization of water and for spraying the atomized water particles onto the surface of the moving paper. None of these methods have proved fully satisfactory.

A prior art electrostatic method has been known in which a high potential is applied to a spray nozzle in order to create an electric field between the spray nozzle and an electrode at ground potential, so as to deposit electrostatically charged water particles onto paper moving between the noule and the electrode. Even so, it remained difficult to impart to the paper a constant homogeneous moisture content. In addition, since a high potential is charged to the spray nozzle, the water supply source connected thereto must be insulated from the ground potential; also, the electrostatic capacity required for operation of this apparatus has been so high as to cause undesirable discharge from every part of the apparatus where the high potential is charged. In addition, the apparatus itself has had to be so huge that it was not appropriate to apply it to a papermanufacturing line.

A primary object of my invention is to provide a method and an apparatus for imparting to moving paper a high or predetermined homogeneous moisture content by aid of an electrostatic force. An important feature of my invention is safety in operation, even though a high potential is employed, for the high potential is charged to only a limited electrode; consequently, the electrostatic capacity required for operation is far less than that of conventional systems, and danger from undesirable discharge is significantly reduced. The water supply and spray systems of this invention are quite simple and compact, and handling and operation is safe.

Another feature of my invention is that the initial spray velocity is reduced, either immediately after spraying or by widening the spray patterns, or by changing the arrangements of spray patterns, so as to adequately overlap the spray patterns.

High efficiency is a third feature of my invention.

The method and apparatus of my invention are safe, simple, compact and reliable, and installation as well as operation is simple. My invention enables stable and continuous operation,

' because of its improved water supply method and the highly efficient mechanism of the apparatus.

The moisture content control range obtained by my invention is fairly wide, 0 to 8 percent by weight of the paper, and more if desired.

The moisture impregnating operation is most efi'ectively accomplished when the apparatus of my invention is used along a paper-manufacturing line, because the paper in such a line has a rather uniform, though low, moisture content. My apparatus can, of course, be applied elsewhere, such as a rerolling section or a printing shop, but the efi'iciency is rather reduced because the paper by that time inevitably has an irregular moisture content, and it is substantially difficult to detect and to modify said irregularity.

In my invention, attracting electrodes charged with a high potential are so made that charged water particles are attracted only to the moving paper without overspray to any other portion. These electrodes are elongated along a line transverse to the moving paper, and the length of the line of electrodes is made equal to or a little bit shorter than the width of the moving paper.

The full nature of my invention will be understood from the following detailed description and the accompanying drawings showing some preferred embodiment of my invention.

In the drawings:

FIG. 1 is a flow diagram illustrating a method embodying the principles of this invention.

FIG. 2 is a flow diagram illustrating a modified method also embodying the principles of the invention.

FIG. 3 is a flow diagram illustrating another modified method embodying the principles of the invention.

FIG. 4 is a view in side elevation of a moisture-imparting system usable in this invention, some of the elements being shown diagrammatically.

FIG. 5 is a view in front elevation of a battery of spray nozzles usable in this invention; the view is broken in the middle to conserve space, another portion being broken away and shown in section.

FIG. 6 is a view in end elevation of the battery of FIG. 5.

FIG. 7 is a view in elevation and partly in section of one spray nozzle.

FIG. 8 is a view in end elevation of the nozzle of FIG. 7.

FIG. 9 is a fragmentary view showing a series of patterns of moisture impingement upon the paper.

FIG. 10 is a view in side elevation of a portion of a paper manufacturing line showing the finishing, moisturizing, and rolling sections.

FIG. 11 is a view at right angles to FIG. 10 of the moisturizing section.

Referring to FIG. I, a certain quantity of slurry pulp is supplied from a stock area 21 to a paper Fourdrinier section 22, from which the wet paper is transferred to a hydro-extracting section 23 and then to a drying section 24. The dried paper, by then in an overdried condition (the moisture content at this stage being only about 4 percent by weight of the paper), may next be transferred to a finishing section 25 where a grazed finish is given to the paper. The graze-finished paper is then, according to this mode of the invention, transferred to an electrostatic moisture impregnating section 26, where moisture is sent to the paper from both sides thereof (about 3 percent moisture by weight of the paper, is added), and then the paper is transferred to a rolling section 27 to be rolled up, the total moisture content of the paper at this stage being about 7 percent by weight of the paper.

The moisture impregnating section 26 need not be provided between the finishing section 25 and the rolling section 27 but can be provided at some other locations along the line of a paper-manufacturing process, as shown in FIGS. 2 and 3. Thus, in FIG. 2 the electrostatic moisture-impregnating section 26 is provided in between the drying section 24 and the finishing section 25, while in FIG. 3, two electrostatic moisture-impregnating sections 26a, 26b are provided, one between the drying section 24 and the finishing section 25 and the other between the finishing section 25 and the rolling section 27. The particular arrangement is determined in accordance with the purpose of moisture impregnation. Thus, when a certain amount of moisture is required to be added to finished paper, the moisture can be provided at a station 26 somewhere between the finishing section 25 and the rolling section 27. On the other hand, to obtain a better glossy finish, the moisture impregnating section 26 should be provided before the paper enters into the finishing section 25. As a third instance, to adjust an irregular moisture content of paper moving out from the drying section 24, a first moisture-impregnating section 26a should be provided between the drying section 24 and the finishing section 25, followed by a second section 26a to raise the total water content. Generally speaking, a homogeneous moisture distribution over the whole area of paper before the finishing section 25 is most desirable in order to obtain a good finish.

Referring to FIG; 4, a strip or sheet of paper is moved in the direction indicated by the arrows. A water supply source 41 at ground potential and compressed air sources 42a and 42b are connected to two spray nozzles 40a and 40b. Thus, two moisture impregnators are provided in order to deposit charged water particles onto the paper from both sides thereof. Water is supplied at a controlled rate to the spraying means for atomization by the compressed air, and atomized water particles are sprayed onto both surfaces of the moving paper. Negative terminals of a high-voltage supply source are connected to electrodes 43a, 43b each having a roller shape that attracts water particles; the electrodes 43a, 43b are supported by bearings 45a, 45b fixed to insulating members 44a, 44b in order to create an electric field between the electrodes and the spraying means. While the moving paper 10 is being passed along the electrodes 43a and 43b in the electric field, finely atomized water particles are attracted onto the moving paper from both sides thereof.

Referring to FIGS. 5 and 6, a spray assembly 51 comprises a plurality of spray nozzles 40, manifolds 53a and 53b for air supply, a main support 54, and a support arm 52 connected to the main support 54. The manifolds 53a and 53b for air supply are in communication with air sources (not shown) and are connected to each spraying device in the manner shown for the nozzle 40 at the left end, and spray nozzles 40 in sufficient number are arranged to cover the whole width of the moving paper with atomized water particles to be deposited thereon.- The spray nozzles 40 may be adjustably mounted in a line on the support arm 52 by means of set screws 61, so as to be able to obtain any desired spray angle against the surfaces of the moving paper. The mounting angles of the spray nozzles 40 are predetermined in accordance with the required size of a spray pattern, and the number of sprays 40 is determined in accordance with the width of the'paper.

FIGS. 7 and 8 show a spray nozzle 40 comprising a set screw 61, a main body 70, a nozzle tip 71, a ring 72, air inlets 80a and 80b, a liquid inlet 81, air-ejecting orifices 84, 85, 86 and a liquid outlet 87. Compressed air is supplied to the spray nozzle 40 from the air inlets 80a and 80b and is ejected from the ejecting orifices 84, 85, 86 through air passages 82a and 82b. Liquid is supplied to a spraying device from the liquid inlet 81 and is ejected from an ejecting orifice 87 through a liquid passage 83 in a form of a spray by compressed air. Compressed air supplied to the air inlet 80b is employed for atomizing water into water particles and spraying the atomized water particles on the moving paper, and the air supplied to the air inlet 80a is employed for adjusting the spray pattern into a required form. Air is preferably supplied to the air inlets from different air sources so as to regulate the air pressure separately according to requirement. A proper air pressure employed for theformer inlet 80b is 0.4 kg./cm.*, and 0.6 kg./cm. is a typical value for the latter inlet 80a. The liquid atomizing air is ejected from the orifice 84, and the spray pattern adjusting air is ejected from the orifice 85. The angle (0) of the spray patterns is adjustable by changing the location of the air-ejecting orifice 85 as by rotating a ring 72 on the perisphere of liquid-ejecting orifice 87; that is, the angle (0) of spray pattern can be changed by inclining the angle of a line passing through the diametrically opposed air-ejecting orifice. The air-ejecting orifices 86 are reserved as auxiliary ones for liquid atomization.

FIG. 9 shows spray patterns 90 created momentarily on a surface of the moving paper 10. As shown in FIG. 9, the individual spray patterns are located parallel to each other and with a certain angular inclination (0) to each other. When the paper moves in this status, spray patterns overlap each other, and a uniform continuous spray pattern can be obtained over the whole area of the moving paper. These spray patterns have been used for the purpose of studying the correlationship of airstreams ejected, from the respective spray nozzles and for getting an optimum spray pattern for moisture impregnation by changing the location of the diametrically opposed airejecting orifices 85. The inclination angle (0) of the spray patterns is adjustable in a range of from 0 to degrees. If the angle is. excessively large or excessively small, it is hardly possible to obtain a proper spray pattern for the purpose of moisture impregnation; that is, if the angle is too small, a certain area between the respective spray patterns is left uncovered with water spray; while if the angle is too large, adjoining sprays interfere with each other and result in the creation of an irregular spray pattern. Neither case can obtain uniform moisture distribution. In actual test runs conducted in a paper manufacturing line, the required homogeneous moisture distribution has been obtained when the angle (8) at 60 degrees, and other angles may also be satisfactory, especially if close to that amount.

In conventional (prior art) spray nozzles, the air supply lines for both the atomization of water and the adjustment of spray patterns have been connected to the same air source and have employed the same air pressure for respective purposes. Subsequently, when the atomizing air pressure was lowered in order to increase the charging efficiency of high electrical potential to the atomized water particles, the air pressure for adjustment of spray patterns was lowered too, and this resulted in narrowing the width of the spray pattern. In my invention, these disadvantages are eliminated by using separate air sources for atomization of water and for adjustment of spray patterns.

ln electrostatic moisture impregnation, it is desirable that the flying speed of the sprayed particles of liquid be as low as possible in order to attain high-attracting efficiency, while the spray pattern should be as wide as possible for covering wide areas on the surface of the moving paper. This is accomplished in my invention with the use of separate air supply lines for liquid atomization and for spray pattern adjustment. Air pressure for liquid. atomization is limited to a certain rate because of the reason above mentioned, and the flow rate of the liquid ejected from a spray nozzle is also restricted to a certain rate. Thus, many spray nozzles must be used for covering the whole area of the surface of moving paper. in other words, the number of spray nozzles to be used is determined by the width of the paper. Generally speaking, the edge portions of the moving paper have less moisture content than does the center portion. Therefore, it is necessary to control the flow rates of the liquid from each spraying device so as to rectify that irregular moisture content, in order to obtain paper having uniform moisture content over the whole area of the paper.

Referring to FIGS. 10 and 11, when the attracting electrodes 43a, 43b are longer than the width of the moving sheet of paper, liquid moisture attracted to extended portions of electrodes not covered with moving paper may form droplets which cause undesirable blackening on the paper; moreover, the droplets result in forming thread lines on the electrodes by the influence of electrostatic force and cause undesirable spark discharges. Therefore, it is desirable that the attracting electrodes be equal to or a little bit shorter than the width of the moving paper.

To those skilled in the art to which this invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the spirit and scope of the invention. The disclosures and the description herein are purely illustrative and are not intended to be in any sense limiting.

I claim:

1. A method of electrostatically impregnating sprayed water particles onto a moving strip of paper, comprising the steps of maintaining at a high potential an attracting roller electrode only that is electrically insulated from ground,

moving the paper along in contact with said electrode, and

air-spraying water onto the moving paper from a predetermined plurality of sprays each maintained at ground potential, and on the opposite side of the paper from the attracting electrode,

said sprays forming an overlapping spray pattern.

2. The method of claim 1 wherein the sprays arespaced parallel with each other across the width of the paper so as to sufficiently cover the whole area of said paper with water particles, said liquid particles thereby being electrostatically deposited on and impregnated in said paper while in an electrostatic field that is created between said sprays and said electrode.

3. The method of claim 1 in which there are two electrodes spaced longitudinally and on opposite sides of the paper with sprays opposite each of them.

4. The method of claim 1 in which each individual spray has an oblong shape inclined to the direction of movement of the paper.

5. The method of claim 1 wherein there are two successive roller electrodes with the identical method steps practiced at each with the spraying done from first one side of said paper strip and then from the other side.

6. A method of electrostatically impregnating air-atomized liquid particles onto moving paper in a line of a paper-manufacturing process having a Fourdrinier stage followed by a hydro-extracting stage followed by a drying stage, comprising the steps of feeding said paper along a negative high-potential roller electrode past the drying stage,

spraying water onto the moving paper in a set of sprays forming an overlapping spray pattern on the opposite side of the paper from the electrode, and

providing water to the sprays from a source maintained at ground potential,

said potential being charged only to said electrode.

7. The method of claim 6 wherein the sprays are spaced relative to said electrode and are arranged in parallel across the width of the paper so as to sufficiently cover the whole area of sad paper with sprayed liquid water particles to be electrostatically deposited on and impregnated in said paper while being passed in an electrostatic field created between said sprays and said electrode.

8. The method of claim 7 wherein each individual spray is projected to provide on the paper an oblong deposit pattern inclined to the direction of movement of the paper with transverse overlay with at least one adjacent spray deposit pattern.

9. The method of claim 6 wherein said method is practiced at each of two roller electrodes, on opposite sides of said paper and by spraying the water from opposite sides of said paper from the electrode at each one.

10. The method according to claim 6 in which each liquid is centered between two streams of air.

11. The method according to claim 6 in which the liquid is atomized by an airstream and the spray pattern is adjusted by another airstream at a higher pressure than that for the atomization.

Hunt 1 mun 

2. The method of claim 1 wherein the sprays are spaced parallel with each other across the width of the paper so as to sufficiently cover the whole area of said paper with water particles, said liquid particles thereby being electrostatically deposited on and impregnated in said paper while in an electrostatic field that is created between said sprays and said electrode.
 3. The method of claim 1 in which there are two electrodes spaced longitudinally and on opposite sides of the paper with sprays opposite each of them.
 4. The method of claim 1 in which each individual spray has an oblong shape inclined to the direction of movement of the paper.
 5. The method of claim 1 wherein there are two successive roller electrodes with the identical method steps practiced at each with the spraying done from first one side of said paper strip and then from the other side.
 6. A method of electrostatically impregnating air-atomized liquid particles onto moving paper in a line of a paper-manufacturing process having a Fourdrinier stage followed by a hydro-extracting stage followed by a drying stage, comprising the steps of feeding said paper along a negative high-potential roller electrode past the drying stage, spraying water onto the moving paper in a set of sprays forming an overlapping spray pattern on the opposite side of the paper from the electrode, and providing water to the sprays from a source maintained at ground potential, said potential being charged only to said electrode.
 7. The method of claim 6 wherein the sprays are spaced relative to said electrode and are arranged in parallel across the width of the paper so as to sufficiently cover the whole aRea of sad paper with sprayed liquid water particles to be electrostatically deposited on and impregnated in said paper while being passed in an electrostatic field created between said sprays and said electrode.
 8. The method of claim 7 wherein each individual spray is projected to provide on the paper an oblong deposit pattern inclined to the direction of movement of the paper with transverse overlay with at least one adjacent spray deposit pattern.
 9. The method of claim 6 wherein said method is practiced at each of two roller electrodes, on opposite sides of said paper and by spraying the water from opposite sides of said paper from the electrode at each one.
 10. The method according to claim 6 in which each liquid is centered between two streams of air.
 11. The method according to claim 6 in which the liquid is atomized by an airstream and the spray pattern is adjusted by another airstream at a higher pressure than that for the atomization. 